The invention relates to an automatically variable drive apparatus including a driving section and a driven section coupled thereto by means of at least one V-belt running over variable diameter pulleys, each pulley comprising a first half-pulley member fixed to a shaft mounted in a housing and rotatable therewith and a second half-pulley member axially slidably disposed over the same shaft, but keyed to it for rotation therewith. Means are provided for adjusting the relative axial positions of the half-pulley members on the shaft for adjusting the diameter of the pulley. These means may comprise, for the driving section for example, centrifugal weights coupled to the shaft and for the driven section, for example, a spring device. The shaft of the driving section is driven by a driving shaft via a conical or bevel gear mounted on the driving shaft which engages with at least one conical or bevel gear, freely rotatable around the shaft of the driving section, selectively coupled for rotation with the shaft and mounted axially and radially in relation to the housing. Such a drive apparatus is generally described in Dutch Pat. No. 95,773.
The driving section of a further development of the known drive apparatus of this type is shown in FIG. 1. Such prior art driving section, provided with two variable diameter pulleys has, as shown in FIG. 1, a single, unitary elongate shaft 1 which is mounted in a housing 4 by means of ball bearings 2 and 3. In this case, a conical gear 5 carried by shaft 1 is mounted thereto by means of a plain bearing 6 while a conical gear 7 is also carried by shaft 1 and is mounted thereto by means of a rolling bearing 8 in the housing 4. Thus, these conical gears 5, 7 are normally rotatable with respect to the shaft 1. The conical gears 5 and 7, which engage a conical gear 9 on the driving shaft 10, can be alternately coupled to the shaft 1 to rotate the same by means of the slidable sleeve 11 which itself is coupled for rotation with shaft 1 by means of splines formed on shaft 1. There are also provided on shaft 1 two variable diameter pulleys which each consist of a half-pulley member 12 fixedly mounted on the shaft 1 for rotation therewith and a half-pulley member 13 axially slidably mounted over shaft 1 by means of the boss sleeve 12a of this half-pulley member 12, but linked for rotation therewith by means of splines formed on shaft 1. The axial position of half-pulley member 13 on shaft 1 and therefore, the effective diameter of the pulley is controlled by the action of centrifugal weights 14.
The driven section of this known embodiment is shown in FIG. 2, and similar to the driving section illustrated in FIG. 1 has a single unitary long shaft 15 on which two adjustable diameter pulleys are mounted, each of which includes a half-pulley member 16 fixedly mounted on the shaft 14 and a half-pulley member 17 axially slidably mounted over shaft 14 by means of the boss sleeve 16a of this half-pulley member 16, but linked for rotation therewith by means of splines formed on the shaft 15. The axial position of half-pulley member 16 is controlled by a pack of springs 18 which are biased against the fixed half-pulley member 16. The pack of springs 18 is coupled on the one hand to the half-pulley member 17 and on the other is coupled to a gear-shaped member 18a which is linked via teeth 15a with the shaft 15.
The disadvantages of this known drive are:
that the maintenance or repair--however minor--of the gearbox require necessary and time-consuming and precise dismantling and reassembly of the entire pulley as well as of the elements coupled with it;
replacement of the driving belt involves a complicated adjustment procedure, in connection with the determination of the correct (new) pitch distance of the pulleys;
the mounting of a pulley on a shaft is fairly complicated, while the use of the various different bearing systems respectively for the shaft, conical gears and housing likewise renders the drive fairly complicated in construction.